Mats are commonly used as borders for framing works of art, such as a photographs, paintings, sketches, and other types of display works. A single mat may be used as a border for the artwork or, alternatively, several mats with different sized openings may be used to form a spectrum of mat borders about the periphery of the framed work. The purpose of a mat border is to enhance the visual appearance of the artwork and to render the frame compatible with the other items in the room.
Mats are generally formed by cutting a window or opening into a full-sized sheet or blank of mat material. The most traditional manner of cutting the windows or openings in mats has been by hand. A person cutting the mat positions a guide along a reference line where the cut is to be made and then passes a cutting blade along the guide to make the cut.
In addition to an opening or window, mats are sometimes decorated with freehand carvings. Such carvings are time-consuming and labor intensive. Sometimes carvings are made using a manual, mat cutting machine, but the shape of such carvings is limited to straight lines, circles, or ovals. These carvings also require much manual labor and time.
A major deficiency with respect to virtually all prior systems for cutting mats relates to overcuts in the mat material. Overcuts have traditionally been required in cutting beveled edges to form the openings.
Another problem encountered in traditional systems of mat cutting is that the mat can be damaged from the clamps that hold the mat to the surface of the cutting table. This problem is accentuated when, as required by most traditional methods, the mat is rotated to effect the typical four cuts required for a rectangular window because the clamps must be repeatedly installed and removed.
One attempt to solve the problems of overcuts has been to place the mat upside down when it is being cut. By so doing, the overcuts will be the most visible from the back of the mat. However, the mat must be inverted before it can be inspected to ensure that a proper cut has been made. Therefore, the overcuts still occur where the two beveled edges of the mat meet at a typical 90.degree. corner of a rectangular frame.
Turning the mat upside down for cutting has served to reduce damage and marks made by clamps. The damage still occurs when clamps are used, although the damaged side is not visible when the mat is placed in the frame. Perhaps more importantly, the mat must be inverted before it can be inspected to ensure that a proper cut has been made.
Another limitation with respect to prior methods of cutting windows in mats relates to the shape of the window. Although some traditional hand-operated cutting devices are capable of cutting circular or oval cuts in mats, the vast majority of mat cutting systems are designed to cut rectangular-shaped windows in mats. For example, U.S. Pat. No. 4,641,556 discloses a mat cutter for cutting rectangular windows in a stock of mats by directing two separate blades in two mutually perpendicular directions to make two perpendicular cuts, rotating the mat 180.degree., then reversing the direction of the two blades to complete the remaining perpendicular cuts. However, this device requires two cutting blades, each with two opposite cutting edges and is limited to cutting rectangular-shaped openings.
A major reason that current mat cutters are so limited in their capabilities is because of the unique problems of cutting beveled edges in the mat. A beveled edge gives the mat a pronounced visual effect inside the frame. Almost all mats are cut with beveled edges (as opposed to vertical edges) at the periphery of the opening or decorative carving. Such beveled edges are generally cut at a 45.degree. angle, relative to the top surface of the mat.
A continuously smooth beveled edge can be cut only when the inclined knife passes through the mat at a constant depth relative to the top surface of the mat. When beveled cuts involve curvilinear edges or intersecting straight edges, it is highly difficult to produce smooth, continuously beveled edges, and intersecting cuts without overcuts. This is especially true with respect to a curvilinear edge that has a reverse curvature, such as an S-shaped edge, and to corner angles other than 90.degree.. Because of this difficulty, traditional cutters cannot make reverse curvature cuts, linear-to-curvilinear cuts, or curvilinear-to-linear cuts in the same operation. It is also the reason they are limited only to making linear, oval, and circular cuts, without the ability to make decorative carvings or openings of various shapes.
Accordingly, there is a need to develop a system for cutting mats lo that is capable of automatically cutting one or more decorative carvings of any shape, including reverse curvature beveled cuts, and openings of any size or shape, including reverse curvature beveled cuts, in a mat, that will cut the openings or carvings with a continuously smooth beveled edge without any overcuts, that does not require any rotation of the mat during cutting, and that can perform such cutting quickly and automatically.
The foregoing deficiencies in traditional mat cutting techniques have been overcome by the present invention, which involves an automatic system for cutting windows, openings, and decorative carvings in mats. The system involves use of a variably positionable head to which a cutting blade is attached for cutting a beveled edge in a mat without any overcuts. A longitudinal drive means, transverse drive means, and orthogonal drive means (i.e., perpendicular to the surface of the mat) form a combined positioning means capable of moving (i.e., translating) the head in any direction. A rotational drive means may also form part of the combined positioning means to rotate the blade and adjust the position of the blade as a linear or curvilinear beveled edge is cut into the mat. A linear variable displacement transducer (LVDT) is coupled to the head and is operatively coupled to the orthogonal drive means to maintain the head a constant distance away from the mat so the blade cuts a continuously smooth beveled edge in the mat. Other objects and advantages of the invention will become apparent from the detailed description of the invention which follows.